Ore separation

ABSTRACT

There is disclosed herein an apparatus for detecting and separating a desired ore or mineral from a quantity of ore. The apparatus includes a plurality of selectively deflectable flowing fluid streams. The streams are controlled to displace the desired mineral particles from the quantity of ore. Pivotally mounted arcuate tubes normally divert the fluid streams when then are not acting to displace particles, but these tubes are selectively movable to allow the streams to hit desired particles. A screen is used for conveying the ore past the fluid streams in such a manner that the streams may act through the screen to displace the selected particles.

United States Patent [1 1 Mathews [4 1 Mar. 27, 1 973 [54] ORESEPARATION [75] Inventor: Ted C. Mathews, San Mateo, Calif.

[73] Assignee: Mathews Mining Company, San

Mateo, Calif.

[22] Filed: Aug. 23, 1971 [21] Appl. No.: 173,776

szj U.S. CL... ..209/74, 209/1115 [51] Int. Cl ..B07c 5/34 [58] Field ofSearch ..209/74, 111.5, 115

[56] References Cited UNITED STATES PATENTS 3,472,375 10/1969 Mathews..209/1 1 1.5 X

Primary Examiner-Allen N. Knowles Assistant ExaminerGene A. ChurchAttorneyLyon & Lyon 2a 24 l Z5 [57] ABSTRACT There is disclosed hereinan apparatus for detecting and separating a desired ore or mineral froma quantity of ore. The apparatus includes a plurality of selectivelydeflectable flowing fluid streams. The streams are controlled todisplace the desired mineral particles from the quantity of ore.Pivotally mounted arcuate tubes normally divert the fluid streams whenthen are not acting to displace particles, but these tubes areselectively movable to allow the streams to hit desired particles. Ascreen is used for conveying the ore past the fluid streams in such amanner that the streams may act through the screen to displace theselected particles.

10 Claims, 4 Drawing Figures PATENTEDmzv-ma 3.722 676 SHEET 2 or 2 INVENTOR. 750 WAfl/aus ORE SEPARATION FIELD OF THE INVENTION Thisinvention relates to ore and mineral separation and more particularly toimproved devices and equipment for separating a desired ore or mineralfrom a quantity of ore.

CROSS-REFERENCE TO RELATED PATENTS Reference is made to U.S. Pat. No.3,356,2ll entitled Ore Separation Process" and U.S. Pat. No. 3,472,375entitled Apparatus and Method for Separating Ore, the disclosures ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION As noted in the above referenced patents,there are known systems for primary separation of valuable and worthlessminerals wherein a difference in physical properties is used to triggera physical separation of the desired mineral. The use of fluid streamsto selectively accomplish the separation function is described, forexample, in said U.S. Pat. No. 3,472,375. The general overall scheme ofsuch systems is to cause crushed or partially crushed ore particles tofall from a moving belt past a sensor. The sensor detects a uniquephysical characteristic of the desired mineral. A unique characteristiccan be imparted to the material by processing the ore in such a way thata physical property associated with the desired ore acquires a secondproperty which is more easily measured. When the measurable property issensed, it triggers means to cause a fluid stream to be activated and toimpinge upon the discriminated particle to physically separate it fromthe main body of ore.

Some systems heretofore imployed in making a primary separation ofminerals have significant limitations based on mandatory requirements onore input. One factor constraining such an input is the speed with whichthe selecting means can separate. This reaction speed affects the volumeof material which can be processed in a given time, and is particularlyimportant when small particles or low grade material is to be separated.The reaction time of the system also may reduce the accuracy ofselection because the process is less able to initiate and terminate aselection response in an almost instantaneous period of time. Withreduced accuracy, the density of'particle input must correspondingly bereduced. The constraint on the density of particles input also reducesthe amount of material which can be processed in a given period of time.

The methods and apparatus disclosed in said above patents provide asignificant improvement over prior separation approaches. However,further improvement is desired in certain cases, such as in theselection of small particles. The selection of small particles isdesirable and important where the mineral is quite valuable, an examplebeing diamonds.

Another factor which acts as a limitation on the input is the need foran accurate trajectory for the particles passing the selection device.When the particles are allowed to fall past the selection device, theiroriginal release should impart a particular velocity to the particles.The particles will then reach the sensor and selection means at apredicted location and time. This is desirable because of the usualreduction in the sensitivity of sensing devices, and the accuracy ofseparating means, as the distance from the desired particles SUMMARY OFTHE INVENTION The present invention involves several novel conceptsparticularly useful in separations where the desired particles arerelatively small. An example, although not intending to be liminedthereby, is the separation of diamonds as small as one twenty thousandthinch. The separation of small particles requires the use of a separationdevice of relatively low mass which can be actuated rapidly, and whichcan be made sufficiently small so as to separate out the desiredparticles without also separating out undesired particles. The presentconcepts accordingly involve means for controlling a flowing fluidstream in a rapid and precise manner. I

A plurality of arcuate tubes are employed to normally divert a likenumber of flowing fluid streams away from the particle selection area.These tubes are pivotally mounted so as to greatly reduce theinertiawhich must be overcome in controlling the fluid streams. In selecting aparticle, an arcuate tube is displaced or moved out of the naturalpathof the flowing stream to allow the stream to impinge upon the particlebeing selected. In this manner the trajectory ofthe selected particle ischanged so that it may be collected in a suitable receptacle. Inasmuchas the arcuate tubes can be made relatively small, and actuated rapidly,they allow-short and precise pulses of fluid to impinge upon the desiredparticles for separation, and function well in separating either wet ordry particles.

Additionally, in the separation of relatively small particles, such asdiamonds as noted above, it is desired to slurry the same with liquid soas to provide a layer approximately one particle size thick on the feedbelt or conveyor. It is difficult to otherwise provide such a thin layerunless the material is completely dry which is difficult to achieve. Onthe other hand, if the material is wet, as it will be when originallyfed as a slurry to the feed belt, the trajectory of the material as itleaves the end of the conveyor will be significantly affected becausemuch of the material will tend to adhere to the belt.

Accordingly, the concepts of the present invention also include the useof a perforated conveyor in the form of a screen. The slurry preferablyis applied to the screen in a layer approximately one particle thick.The screen type belt allows the liquid from the slurry to drain off asthe material is conveyed to the detection and separation area. The useof a screen also allows separation of the desired particles through thebelt. The

- belt conveys the material past sensors which detect the characteristicof the desired particles, such as radiation thereof or radiation from apreferential coating thereon as described in said above patents. Thearcuate tubes are mounted under the belt and are actuated in response tothe signals from the sensing system to cause liquid to flow through thescreen belt and deflect desired particles therefrom into a receptacle.This arrangement eliminates the problems associated with developing adesired trajectory for the particles. The screen arrangement furtherallows the material tobe introduced in either a wet state or a drystate, and allows the use of a wide range of belt feed speeds.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration ofthe separating apparatus according to the present invention showing anarcuate tube in a position to normaliy deflect flowing liquid streamsaway from the separation area;

FIG. 2 is a similar illustration showing an arcuate tube displaced toallow a flowing stream to impinge upon, and thus change the trajectoryof, a desired particle; I

FIG. 3 is a detailed side elevational view of apparatus similar to thatof FIGS. 1 and 2 but including a screen type conveyor; and

FIG. 4 is a partial perspective view of the arrangement of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 schematicallyillustrate apparatus according to the present concepts employing aplurality of pivotally mounted arcuate tubes which are used to normallydeflect'a like plurality of continuously flowing liquid streams, butwhich may be moved or otherwise displaced about a pivot axis to allowone or more streams to impinge upon one or more respective desiredparticles to be separated. FIGS. 3 and-4 illustrate construction detailsof this arrangement, and further illustrate its use in conjunction witha moving screen type conveyor or belt wherein the deflecting apparatusis mounted beneath the belt to displace desired particles from the beltrather than accomplishing this operation during free-fall of theparticles as schematically illustrated in FIGS. 1 and 2. The latterscreen type belt arrangement is particularly advantageous, as notedearlier, where particles are wet, in in a slurry, or otherwise moistwhereby the mormal free-fall trajectory thereof would be affected bytheir tendency to adhere to the belt when falling therefrom. Thisarrangement is particularly suitable for fine particle separations whichliquid fluorescent material, as more particularly described in saidaforementioned patents. A sensor 14 is located adjacent the trajectoryplane 12 and generates a timed response when a desired or preferredparticle passes any one of many discrete areas of observation across thetrajectory plane 12 respectively associated with the plural tubes.

The sensor response is supplied to one of a bank of double actingactuators 16 which are mechanically linked to pivotally mounted arcuatetubes 18. A typical conveyor belt is 30 to 40 inches wide and, thus, alarge plurality of actuators and tubes are employed to select particlesfalling from any point along the width of the belt; likewise, the sensor14 includes a like plurality of sensors to completely cover the plane 12of interest. That is, there is a sensor corresponding to each tube, eachsensor observing the area of its respective tube. The actuators 16 serveto pivot respective arcuate tubes 18,to the position shown in FIG. 2 andto return v the tubes to the normal position shown in FIG. 1. Conhavebeen applied to the belt in a slurry, and is particu- .larly usefulforseparation of diamonds and diamond particles fromother materiaL- Turningnow to a discussion of FIGS. 1 and 2, a conveyor 10 is shown onto whichore material is applied for feeding the ore into a trajectory planesymbolicallyillustrated by an arrow 12. In separating desired materials,the latter have a measurable property not possessed by the othermaterial fed to the conveyor. Examples of such property are naturalradiation, or fluorescence imparted by minerals to electromagneticradiation to cause at least a portion thereof to fluorescence at acharacteristic wavelength. The latter can be achieved by preferentiallycoating some of the particles with a tinuous fluid streams are suppliedto the inlet ends of the arcuate tubes 18 from a manifold 20 throughrespective nozzles 22. I

In the normal or non-selection mode as illustrated in FIG. 1, thearcuate tubes 18 are positioned relative to the streams so that eachstream is chanelled through a corresponding arcuate tube 18 onto adeflection plate 24 which diverts the fluid from the system. In thismode, the ore particles fall along the trajectory plane 12 and into anore receptacle 26. When the sensor 14- observes a particle which is tobe separated from the main body of the ore, the sensor 14 responds tothe observation by triggering the appropriate actuator 16. The actuatorpivots its respective arcuate tube 18 for the sensed area away from thecontinuous fluid stream thereby allowing thestream to directly impingeupon the selected particle, causing the particle to be diverted into themineral receptacle 28. With a 40 inch wide belt approximately 320actuators 16, tubes 18 and nozzles 22 are employed, and the sensor 14includes a like number of detectors.

With typical separating apparatus for separating relatively smallparticles, such as diamonds as noted earlier, the arcuate tubes 18 aremounted apart on A; inch centers, and the water jet from eachnozzle 22is approximately 1/16 inch in diameter. The conveyor belt may beapproximately 30 inches wide.

The arcuate tube arrangement is particularly advantageous in providing afast acting deflection system. The arcuate tubes can be made relativelysmall and light weight so that the same can be moved rapidly by anelectromagnetic actuator 16. Furthermore, in the normal position shownin FIG. 1, the .water flow through the arcuate tube 18 tends to maintainthe tube I in the fluid-deflecting position as shown, but when thearcuate tube is' partially deflected (rotated counterclockwise as seenin FIGS. 1 and 2) by the actuator 16,

the fluid jet on the entry end of the tube from the nozzle 22 andpartial amount of fluid remaining toward the outlet end of the tube aidsin quickly deflecting the 18 when the entry end of the tube interceptsthe fluid stream.

Turning now to a more detailed description of the concepts of thepresent invention, and particularly to the arrangement illustrated inFIGS. 3 and 4, there is shown a screen type conveyor 30 and the sensor14 mounted above the screen, and the actuator assembly mounted beneaththe screen for deflecting desired particles therefrom rather thandeflecting the particles from the free-fall trajectory 12 upon leavingthe conveyor as illustrated in FIG. 1. Even material such as l/2 inchparticles, tends to stick to a belt when wet thereby adversely affectingthe trajectory thereof. The sensor 14 may be any of several types ofsensors incorporating a plurality of sensing elements across the lateraldimension, or width, of the conveyor for sensing the uniquecharacteristic of desired particles. Exemplary sensing arrangements aredisclosed in said aforementioned patents. Suitable sensing devicesinclude electromagnetic radiation sensors, color sensors, reflectivitysensors, radioactivity sensors, thermo-magnetic sensors, and the like.The sensing system employed is principally dictated by thecharacteristics of the ore to be separated.

The sensor 14 includes a row of individual sensing units, as notedabove, the number and spacing thereof depending upon the width of theconveyor and the size of the particles to be selected, in order todetermine the lateral location of such particles on the screen 30, or inthe trajectory plane 12 if the free-fall arrangement of FIGS. 1 and 2 isused. Furthermore, the sensor system 14 includes appropriate electricalcircuits for detecting the responses of the respective sensing elementsupon detection of a desired particle, and for translating such signalsinto respective gating signals timed to actuate the selection system atthe appropriate instant, and to allow or enable return of the selectionsystem to its normal state following the selection. An exemplary systemand sircuits are described and illustrated in said U.S. Pat. No.3,472,375. The arrangement thereon illustrated describes an exemplaryarrangement wherein ore has been treated with a fluorescent material, isirradiated by a radiation source, and the characteristic radiationemitted by desired particles of ore is-detected by an electromagneticwave sensing means, such as a plurality of photomultiplyers. The sensingor detecting means then provides signals to an amplifier and controlcircuit which in turn actuates one or more electromagnetic actuators,the particular one or more actuated depends upon the number'and positionof desired'particles when were detected. These actuators, according tosaid U.S. Pat; No. 3,472,375, then pivot tubes flexibly coupled with amanifold to supply a stream of fluid for deflecting the desired particleor particles from the nor mal trajectory thereof. 1

The use of arcuate tubes 18 allows a more closely spaced selectionapparatus and eliminates the need for flexible connections. These tubesmay be operated in any suitable manner, such as by means ofelectromagnetic actuators of the nature of those illustrated in saidU.S. Pat. No. 3,472,375. Any other suitable arrangement may be employed,such as a staggered'arrangement of groups of electromagnetic actuators34 and 36 mounted approximately 90 apart, each of which is double actingfor moving its respective tube in two directions. These actuators arestaggered to allow a more compact, or close, spacing of the tubes. Thusthe actuators 34 operate the first, third, fifth, etc., tubes and theactuators 36 operate the second,-fourth, sixth, etc., tubes. As will beapparent from an examination of FIG. 3, energization of actuator 34 willpivot the arcuate tube 18 counter-clockwise and thus allow a stream offluid, such as water, from the nozzle 22 to flow through the screen 30and impinge upon a particle thereon. Reverse energization of theactuator 34 will return the tube to its normal, fluid deflecting,position. The actuator 36 similarly rotates the next arcuate tube. Anyother suitable arrangement for moving the arcuate tubes 18 may beemployed, such as a pair of single-acting electromagnetic actuatorscoupled to each tube, one actuator for moving the tube in one directionand the other actuator for moving the tube in the other direction; asingle actuator 34 or 36 for pivoting the tube 18 counter-clockwise anda spring for returning it to its normal position; and the like. Thearrangement as illustrated in FIG. 3 employs mechanical linkages '38 and40 for the respective actuators 34 and 36. These linkages may be formedof wire. Finer wire. may be used if pairs of single-acting actuators areused for each tube inasmuch as both actuators in this case operate in apull mode only rather than in a push-pull, or doubleacting, mode. Whererelatively fine. particles are to be separated, it is, of course,desirable that the plurality of actuators employed be relatively compactin the lateral dimension, or width dimension, of the conveyor screen 30.In this regard, instead of employing cylindrical coil type actuatorsother configurations can be used, such as a plurality of flat coilsmounted on relatively thin forms to allow close center-to-center spacingof the actuatorsand arcuate tubes 18.

Each arcuate tube 18 is secured to a suitable bracket 41 and thelinkages 38 and 40 are pivotally coupled with'the brackets forrespective pairs of tubes at 42 and 43. That is, the'linkages 38 areconnected at the lower ends of the brackets at 42 for the first, third,etc., tubes; whereas, the linkages 40 are connected at the upper ends ofthe brackets at 43 for the second, third, etc. tubes. Pivot rings 46 aresecured to the arcuate tubes 18, and these rings are pivotally mountedon a rod 48. The rings 46 are mounted at a position on the arcuate tubes18 so as not to interfere with fluid streams from the nozzles 22. Theradius of the tubes 18 is selected to sufflciently divert the fluidstreams so that the streams will not come in contact with the orewhenthe tube is in a normal, fluid deflecting, position as indicated atFIG. 1 so as to prevent inadvertant selection of worthless material.Similarly, the stroke of each actuator 34 and 36 is selected to providesufficient clearence in swinging the upper end of a respective tube 18from the path of a stream from a nozzle.22 upon. particle selection. Thenumber of arcuate tubes l8'is selected to correspond with the number ofsensing elements in the sensor system 14, and is sufficient to cover thewidth of the selection area. With a 30 inch wide screen, an arrangementfor selecting relatively small particles as described previously mayinclude approximately 240 arcuate tubes 18 mounted on inch centersacross the width of the screen.

A receptacle or collection box 54 is located relatively close to theouter surface of the screen 30, and exand precise positioning thereofare dependent upon the.

size and weight of the desired particles to be selected.

Where a screen 30 is employed, and particularly with a slurry ofmaterial, it has been found to be particularly advantageous to arrangethe portion of the screen 30 in .the selection area at an angle asillustrated in FIG. 3.

The greater the angle 6 the easier it becomes to lift or deflectparticles from the surface of the screen 30 to the receptacle 34.Conversely, if the angle becomes too great, the particles tend toaccelerate down the screen 30 in a partial free-fall or free-roll andmove too quickly to be hit by streams from the nozzles 22. On the otherhand, the smaller the angle 0, the greater the force required to deflectthe particles from the screen.

With wet material, for example, the trajectory of the material fallingfrom the screen is relatively unpredictable as noted earlier; on theother hand, it is relatively crushed, and put through heavy mediaseparation to derive a material having particle sizes in the rangedesired. This material is slurred with water to provide a dispersionsufficient to spread on the screen, such as approximately two to fiveparts of water per one part material, and then is spread on the feed endof the screen belt 30 in a thin layer approximately one particle sizethick. The screen has openings of approximately one-twenty thousandthinch, and allows dewatering of the slurry without loss of the material.The screen 30 may be approximately 30 inches wide and be formed ofstainless steel thirteen thousandths diameter wire, and

' be moved at approximately 400- feet perminute. The

difficult to selectively remove desired particles from a 1 horizontalportion of the screen. With the angled arrangement of FIG. 3, with 6being approximately 45 for example, the force of gravity on retainingparticles on the screen is reduced by approximately 50 to 80 percent.This reduces the force required in deflecting a particle from the outersurface of the screen, while obviating the problems of sensing anddeflecting particles freely falling from the screen. The angle of thebelt in the separation area also aids in collecting particles in thecontainer 54. The angled portion of the screen may be providedbyemploying single or plural (so as not to abruptly change the directionof the belt) rollers at upper and lower locations 60 and 61.

The screen size or mesh is determined by the minimum particle sizedesired to be separated. The optimum size isthat which will barelyretain the smallest desired particle on the screen. With a coarserscreen, the fluid streams are more effective in deflecting particlestherefrom.

Although not intended to be limited thereby, an example of constructionand operation of the apparatus in FIGS. 3-4 for use in diamondseparation will be described. Typical prior separation devices do notseparate particles less than is inch in size, and it is necessary thatthe material be dry. However, in the separation of diamonds and similarminerals it is economically'feasible to separate relatively smallparticles, such as down to one-twenty thousandth inch and smaller. Thus,although the value-of the material should be relatively high to makeseparation of fine particles economical, the concentration of diamondparticles in the ore material does not have to be great inasmuch as aneconomicaland efficient separation can take place according to thepresent concepts. Inseparating diamonds as small as one-twentythousandth of an inch, the screen belt has approximately one-twentythousandth inch openings. The orematerial is mined,

tubes 18 may be mounted on approximately 1s inch centers. The desiredmaterial such as diamonds as noted above, are preferentially coated witha fluorescent agent prior to slurrying or as part of the slurry.

The sensor 14 is mounted relatively close to the layer of material, andpreferably as close as possible inand at a belt speed of 400.feet perminute, approximately 6 feet of belt prior to thedetecting andseparating area thereof is sufficient to allow the material tosufficiently drain, unless. the material includes clay which requires alonger draining time. Each arcuate tube 18 may have an inside diameterof approximately 1/16 inch and a radius of approximately 2 inches, withthe pivot at. rod 48 falling on a radial line essentially half-waybetween the ends of the tube.

The present embodiments of this invention are to be considered in allrespects as illustrative and not restrictive, the scope of the inventionbeing indicated by the appended claims rather than the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims therefore are intended to be embraced therein.

What is claimed is: 1. Apparatus for separating first and second solidparticles wherein the first type particle has a particular measurablecharacteristic, comprising means for moving the first and 'secondparticles in a uniform path,

sensing means for detecting the measurable charac teristic of the firsttype particle and for providing control signals,

nozzle means for forming a plurality of flowing fluid streams, andplurality of separating means responsive to said signals for allowingselective impingement of the flowing fluid streams on the first type ofparticle to separate the first type of particles from the second type ofparticle, said plurality of separating means each including an actuatorcoupled with pivotally mounted arcuate means, said actuator beingresponsive to a control signal for moving said arcuate means from anormal position to another position for allowing said selectiveimpingement of a flowing fluid stream from a nozzle means on a firsttype of particle.

2. The apparatus of claim 1, wherein said means for moving theunseparated ore particles in a uniform path includes perforated conveyormeans through which said fluid streams can pass to impinge upon thefirst type particles.

3. The apparatus of claim 2 wherein the conveyor means has an inclinedseparation area, said separating means being mounted beneath saidconveyor means to cause fluid streams to flow through said inclinedseparation area.

4. The apparatus of claim 1 wherein each of said plurality of arcuatemeans comprises a pivotally mounted arcuate tube, said actuators beingactuated by said control signals to rotate each of said tubesindependently into and out of the path of a respective flowing fluidstream from said nozzle means. 5. The apparatus of claim 1 wherein saidarcuate means includes a plurality of arcuate tubes pivotally mountedand positioned to normally intercept and deflect the respective flowingfluid streams from said nozzle means, and the actuators coupled withsaid tubes selectively pivot respective tubes out of the paths of saidflowing streams. 6. Apparatus for separating first and second types ofore particles wherein the first type of ore particles has a measurableproperty not associated with the second type of ore particles comprisinga screen conveyor having an inclined separation section,

sensing means extending across the width of said section for detectingthe measurable property of the first type of ore particles along saidwidth and providing control signals,

means forming a plurality of flowing fluid streams,

.a plurality of separating means extending along the width of saidsection on an opposite side of said section from said sensing means,said separating means being responsive to said signals for causing theflowing fluid streams to flow through said conveyor to provide selectiveimpingement of the flowing fluid streams on the first type of particlesto separate the first type of particles from the second type ofparticles.

7. The apparatus of claim 6 wherein said separating means comprises aplurality of arcuate tubes through which the fluid streams normally passand which are selectively pivotable to allow fluid streams to flowthrough said conveyor.

8. Apparatus as in claim 6 wherein said conveyor has a relatively flatsection preceeding said inclined separation section, and

said sensing means is mounted above said separation section and saidseparating means are mounted below said separation section.

9. The apparatus of claim 6 wherein said separating means includes aplurality of actuators coupled with a respective plurality of pivotallymounted arcuate tubes, said actuators being responsive to saidcontrolsignals from said sensing means to rotate respective tubesindependently into and out of the path of respective flowing fluidstreams.

10.Apparatus as in claim 6 wherein said separating means are mountedbeneath said separation section of said conveyor, and

said separating means includes a pluralityof pivotally mounted arcuatetubes positioned to normally intercept and deflect the respectiveflowing fluid streams, and includes actuators coupled with said tubes toselectively pivot respective tubes out of the paths of said flowingstreams in response to control signals from said sensing means.

1. Apparatus for separating first and second solid particles wherein thefirst type particle has a particular measurable characteristic,comprising means for moving the first and second particles in a uniformpath, sensing means for detecting the measurable characteristic of thefirst type particle and for providing control signals, nozzle means forforming a plurality of flowing fluid streams, and a plurality ofseparating means responsive to said signals for allowing selectiveimpingement of the flowing fluid streams on the first type of particleto separate the first type of particles from the second type ofparticle, said plurality of separating means each including an actuatorcoupled with pivotally mounted arcuate means, said actuator beingresponsive to a control signal for moving said arcuate means from anormal pOsition to another position for allowing said selectiveimpingement of a flowing fluid stream from a nozzle means on a firsttype of particle.
 2. The apparatus of claim 1, wherein said means formoving the unseparated ore particles in a uniform path includesperforated conveyor means through which said fluid streams can pass toimpinge upon the first type particles.
 3. The apparatus of claim 2wherein the conveyor means has an inclined separation area, saidseparating means being mounted beneath said conveyor means to causefluid streams to flow through said inclined separation area.
 4. Theapparatus of claim 1 wherein each of said plurality of arcuate meanscomprises a pivotally mounted arcuate tube, said actuators beingactuated by said control signals to rotate each of said tubesindependently into and out of the path of a respective flowing fluidstream from said nozzle means.
 5. The apparatus of claim 1 wherein saidarcuate means includes a plurality of arcuate tubes pivotally mountedand positioned to normally intercept and deflect the respective flowingfluid streams from said nozzle means, and the actuators coupled withsaid tubes selectively pivot respective tubes out of the paths of saidflowing streams.
 6. Apparatus for separating first and second types ofore particles wherein the first type of ore particles has a measurableproperty not associated with the second type of ore particles comprisinga screen conveyor having an inclined separation section, sensing meansextending across the width of said section for detecting the measurableproperty of the first type of ore particles along said width andproviding control signals, means forming a plurality of flowing fluidstreams, a plurality of separating means extending along the width ofsaid section on an opposite side of said section from said sensingmeans, said separating means being responsive to said signals forcausing the flowing fluid streams to flow through said conveyor toprovide selective impingement of the flowing fluid streams on the firsttype of particles to separate the first type of particles from thesecond type of particles.
 7. The apparatus of claim 6 wherein saidseparating means comprises a plurality of arcuate tubes through whichthe fluid streams normally pass and which are selectively pivotable toallow fluid streams to flow through said conveyor.
 8. Apparatus as inclaim 6 wherein said conveyor has a relatively flat section preceedingsaid inclined separation section, and said sensing means is mountedabove said separation section and said separating means are mountedbelow said separation section.
 9. The apparatus of claim 6 wherein saidseparating means includes a plurality of actuators coupled with arespective plurality of pivotally mounted arcuate tubes, said actuatorsbeing responsive to said control signals from said sensing means torotate respective tubes independently into and out of the path ofrespective flowing fluid streams.
 10. Apparatus as in claim 6 whereinsaid separating means are mounted beneath said separation section ofsaid conveyor, and said separating means includes a plurality ofpivotally mounted arcuate tubes positioned to normally intercept anddeflect the respective flowing fluid streams, and includes actuatorscoupled with said tubes to selectively pivot respective tubes out of thepaths of said flowing streams in response to control signals from saidsensing means.